Three-dimensional nano-structure array

ABSTRACT

A three-dimensional nano-structure array includes a substrate and a number of three-dimensional nano-structures. Each three-dimensional nano-structure has a first peak and a second peak aligned side by side. A first groove is defined between the first peak and the second peak. A second groove is defined between the two adjacent three-dimensional nano-structures. A depth of the first groove is lower than that of the second groove.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 fromChina Patent Application No. 201110292904.2, filed on Oct. 6, 2011 inthe China Intellectual Property Office, disclosure of which isincorporated herein by reference. This application is related toapplications entitled, “METHOD FOR MAKING THREE-DIMENSIONALNANO-STRUCTURE ARRAY”, filed ______ (Atty. Docket No. US41768); “METHODFOR MAKING LIGHT EMITTING DIODE”, filed ______ (Atty. Docket No.US41908); “LIGHT EMITTING DIODE”, filed ______ (Atty. Docket No.US41909); “METHOD FOR MAKING LIGHT EMITTING DIODE”, filed ______ (Atty.Docket No. US41910); “LIGHT EMITTING DIODE”, filed ______ (Atty. DocketNo. US41911); “METHOD FOR MAKING LIGHT EMITTING DIODE”, filed ______(Atty. Docket No. US41912); “LIGHT EMITTING DIODE”, filed ______ (Atty.Docket No. US41913).

BACKGROUND

1. Technical Field

The present disclosure relates to a three-dimensional nano-structurearray and a method for making the same.

2. Description of Related Art

Nano materials can be one-dimensional such as carbon nanotube, ortwo-dimensional such as grapheme. A three-dimensional nano-structure,such as a three-dimensional nano-structure array, is difficult tofabricate. A method for making the three-dimensional nano-structurearray usually includes lithographing. However, the cost of lithographyis expensive, and the three-dimensional nano-structure fabricationprocess is complicated.

What is needed, therefore, is to provide a three-dimensionalnano-structure array and a low-cost and simple method for making thesame.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is an isometric view of one embodiment of a three-dimensionalnano-structure array.

FIG. 2 is a cross-sectional view, along a line II-II of FIG. 1.

FIG. 3 is a Scanning Electron Microscope (SEM) image of FIG. 1.

FIG. 4 shows a process of one embodiment of a method for making athree-dimensional nano-structure array.

FIG. 5 shows a process of one embodiment of forming a three-dimensionalnano-structure array perform in the method of FIG. 4.

FIG. 6 is an SEM image of a three-dimensional nano-structure arraypreform of FIG. 5.

FIG. 7 is a top view of one embodiment of a three-dimensionalnano-structure array.

FIG. 8 is a cross-sectional view, along a line VIII-VIII of FIG. 7.

FIG. 9 is a top view of one embodiment of a three-dimensionalnano-structure array.

FIG. 10 is a cross-sectional view, along a line X-X of FIG. 9.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

References will now be made to the drawings to describe, in detail,various embodiments of the present three-dimensional nano-structurearrays and methods for making the same.

Referring to FIGS. 1 and 2, one embodiment of a three-dimensionalnano-structure array 10 includes a substrate 100 and a plurality ofthree-dimensional nano-structures 102 located on at least one surface ofthe substrate 100. Each of the three-dimensional nano-structures 102 hasan M-shaped cross-section. The three-dimensional nano-structure 102having the M-shaped cross-section will be referred to as an M-shapedthree-dimensional nano-structure 102 hereinafter.

The substrate 100 can be an insulative substrate or a semiconductorsubstrate. The substrate 100 can be made of glass, quartz, silicon (Si),silicon dioxide (SiO₂), silicon nitride (Si₃N₄), gallium nitride (GaN),gallium arsenide (GaAs), alumina (Al₂O₃), or magnesia (MgO). Thesubstrate 100 can also be made of a doped material such as doped N-typeGaN or P-type GaN. A size and a thickness of the substrate 100 can bedetermined according to need. In one embodiment, the substrate 100 is asquare sapphire substrate with a GaN semiconductor epilayer grownthereon. A side length of the substrate 100 is about 2 centimeters.

The plurality of three-dimensional nano-structures 102 can be aprotruding structure, protruding out from the surface of the substrate100. The material of the three-dimensional nano-structures 102 can bethe same as or different from the material of the substrate 100. Thethree-dimensional nano-structure 102 can be attached on the surface ofthe substrate 100, and the three-dimensional nano-structure 102 can alsobe integrated with the substrate 100 to form an integrated structure.

The plurality of three-dimensional nano-structures 102 can be arrangedside by side. Each three-dimensional nano-structure 102 can extend alonga straight line, a curvy line, or a polygonal line. The extendingdirection is substantially parallel with the surface of the substrate100. The two adjacent three-dimensional nano-structures are arrangedwith a certain interval. The distance ranges from about 0 nanometers toabout 200 nanometers. The extending direction of the three-dimensionalnano-structure 102 can be fixed or varied. If the extending direction ofthe three-dimensional nano-structure 102 is fixed, the plurality ofthree-dimensional nano-structures 102 extends substantially along astraight line. In other cases, the three-dimensional nano-structures 102extends along a polygonal line or a curvy line. The cross-sectional viewof the three-dimensional nano-structure 102 along the extending, is inthe shape of an “M” with the same area. Referring to FIG. 3, thethree-dimensional nano-structures 102 are a plurality of bar-shapedprotruding structures extending along a straight line and spaced fromeach other. The plurality of three-dimensional nano-structures 102 aresubstantially parallel with each other and extend substantially alongthe same direction to form an array. The plurality of three-dimensionalnano-structures 102 are uniformly and equidistantly distributed on theentire surface of the substrate 100.

The extending direction of the three-dimensional nano-structure 102 isdefined as the X direction, and the Y direction is substantiallyperpendicular to the X direction and substantially parallel with thesurface of the substrate 100. The three-dimensional nano-structure 102extends from one side of the substrate 100 to the opposite side alongthe X direction. The three-dimensional nano-structure 102 is adouble-peak structure including two peaks. The cross-section of thedouble-peak structure is in the shape of M. Each M-shapedthree-dimensional nano-structure 102 includes a first peak 1022 and asecond peak 1024. The first peak 1022 and the second peak 1024 extendsubstantially along the X direction. The first peak 1022 includes afirst surface 1022 a and a second surface 1022 b. The first surface 1022a and the second surface 1022 b intersect to form an intersection lineand an included angle θ with the first peak 1022. The intersection linecan be a straight line, a curvy line, or a polygonal line. The includedangle θ is greater than 0 degrees and smaller than 180 degrees. In oneembodiment, the included angle θ ranges from about 30 degrees to about90 degrees. The first surface 1022 a and the second surface 1022 b canbe planar, curvy, or wrinkly. In one embodiment, the first surface 1022a and the second surface 1022 b are planar. The first surface 1022 aintersects the surface of the substrate 100 at an angle α. The angle αis greater than 0 degrees and less than or equal to 90 degrees. In oneembodiment, the angle α is greater than 80 degrees and small than 90degrees. The first surface 1022 a includes a side connected to thesurface of the substrate 100, and extends away from the substrate 100intersecting with the second surface 1022 b. The second surface 1022 bincludes a side connected with the second peak 1024 and extends awayfrom the substrate 100 at an angle β. The angle β is greater than 0degrees and smaller than 90 degrees.

The second peak 1024 includes a third surface 1024 a and a fourthsurface 1024 b. The structure of the second peak 1024 is substantiallythe same as that of the first peak 1022. The third surface 1024 a andthe fourth surface 1024 b intersect with each other to form the includedangle with the second peak 1024. The third surface 1024 a includes aside intersected with the surface of the substrate 100, and extends awayfrom the substrate 100 to intersect with the fourth surface 1024 b. Thefourth surface 1024 b includes a side intersected with the third surface1024 a to form the included angle of the second peak 1024, and extendsto intersect with the second surface 1022 b of the first peak 1022 todefine a first groove 1026. A second groove 1028 is defined between twoadjacent three-dimensional nano-structures 102. The second groove 1028is defined by the third surface 1024 a of the second peak 1024 and thefirst surface 1022 a of the first peak 1022 of the adjacentthree-dimensional nano-structure 102.

The first peak 1022 and the second peak 1024 protrude out of thesubstrate 100. The height of the first peak 1022 and the second peak1024 is arbitrary and can be selected according to need. In oneembodiment, both the height of the first peak 1022 and that of thesecond peak 1024 range from about 150 nanometers to about 200nanometers. The height of the first peak 1022 can be substantially equalto that of the second peak 1024. Both the first peak 1022 and the secondpeak 1024 have the highest point. The highest point of the first peak1022 and the second peak 1024 is defined as the farthest point away fromthe surface of the substrate 100. In one three-dimensionalnano-structure 102, the highest point of the first peak 1022 is spacedfrom that of the second peak 1024 with a certain distance ranging fromabout 20 nanometers to about 100 nanometers. The first peak 1022 and thesecond peak 1024 extend substantially along the X direction. Thecross-section of the first peak 1022 and the second peak 1024 can betrapezoidal or triangular, and the shape of the first peak 1022 and thesecond peak 1024 can be the same. In one embodiment, the cross-sectionof the first peak 1022 and the second peak 1024 is in the shape of atriangle. The first peak 1022 and the second peak 1022 form thedouble-peak structure. In one embodiment, the first peak 1022, thesecond peak 1024, and the substrate 100 form an integrated structure.Because of the limitation of the technology, the first surface 1022 aand the second surface 1022 b cannot be absolutely planar.

In each M-shaped three-dimensional nano-structure 102, the first peak1022 and the second peak 1024 define the first groove 1026. Theextending direction of the first groove 1026 is substantially the sameas the extending direction of the first peak 1022 and the second peak1024. The cross-section of the first groove 1026 is V-shaped. The depthh₁ of the first groove 1026 in different three-dimensionalnano-structures 102 is substantially the same. The depth h₁ is definedas the distance between the highest point of the first peak 1022 and thebottom of the first groove 1026. The depth of the first groove 1026 issmaller than the height of the first peak 1022 and the second peak 1024.

The second groove 1028 extends substantially along the extendingdirection of the three-dimensional nano-structures 102. Thecross-section of the second groove 1028 is V-shaped or inversetrapezium. Along the extending direction, the cross-section of thesecond groove 1028 is substantially the same. The depth h₂ of the secondgroove 1028 between each two adjacent three-dimensional nano-structures102 is substantially the same. The depth h₂ is defined as the distancebetween the highest point and the bottom of the second groove 1028. Thedepth h₂ of the second groove 1028 is greater than depth h₁ of the firstgroove 1026, and the ratio between h₁ and h₂ ranges from about 1:1.2 toabout 1:3 (1:1.2≦h₁:h₂≦1:3). The depth h₁ of the first groove 1026ranges from about 30 nanometers to about 120 nanometers, and the depthh₂ of the second groove 1028 ranges from about 90 nanometers to about200 nanometers. In one embodiment, the depth of the first groove 1026 isabout 80 nanometers, and the depth of the second groove 1028 is about180 nanometers. The depth of the first groove 1026 and the second groove1028 can be selected according to need.

The width λ of the three-dimensional nano-structure 102 ranges fromabout 100 nanometers to about 200 nanometers. The width λ of thethree-dimensional nano-structure 102 is defined as the maximum span ofthe three-dimensional nano-structure 102 along the Y direction. The spanof the three-dimensional nano-structure 102 gradually decreases alongthe direction away from the substrate 100. Thus, in eachthree-dimensional nano-structure 102, the distance between the highestpoint of the first peak 1022 and that of the second peak 1024 is smallerthan the width of the three-dimensional nano-structure 102. Theplurality of three-dimensional nano-structures 102 can be distributedwith a certain interval, and the interval can be substantially the same.The interval forms the second groove 1028. The distance λ₀ between thetwo adjacent three-dimensional nano-structures 120 ranges from about 0nanometers to about 200 nanometers. The distance between each twoadjacent three-dimensional nano-structures 120 can be substantially thesame. The distance λ₀ can be increased or decreased with the increase ordecrease of the height of the first peak 1022 and the second peak 1024.In the Y direction, the distance λ₀ can be gradually increased,decreased, or periodically varied. If the distance λ₀=0, thecross-section of the second groove 1028 is V-shaped. If the distanceλ₀>0, the cross-section of the second groove 1028 is in the shape of aninverse trapezium.

Along the Y direction, the plurality of three-dimensionalnano-structures 102 is distributed in a certain period P. One period Pis defined as the width of the three-dimensional nano-structures 102 λadded with the distance λ₀. The period P of the plurality ofthree-dimensional nano-structures 102 can range from about 100nanometers to about 500 nanometers. The period P, the width λ and thedistance λ₀ satisfy the following formula: P=λ+λ₀. The period P, thewidth λ and the distance λ₀ are measured in nanometers. The period P canbe a constant, and λ₀ or λ can be a dependent variable. Furthermore, onepart of the three-dimensional nano-structures 102 can be aligned in afirst period, and another part of the three-dimensional nano-structures102 can be aligned in a second period. In one embodiment, the period Pis about 200 nanometers, the width λ is about 190 nanometers, and thedistance λ₀ is about 10 nanometers.

The three-dimensional nano-structure array 10 includes the plurality ofM-shaped three-dimensional nano-structures 102, thus the M-shapedthree-dimensional nano-structures can be two layers of three-dimensionalnano-structures assembled together. The plurality of M-shapedthree-dimensional nano-structures 102 can be used in many fields such asnano-optics, nano-integrated circuits, and nano-integrated optics.

Referring to FIG. 4, one embodiment of a method for making athree-dimensional nano-structure array 10 includes the following steps:

step (S10), providing a base 101;

step (S11), locating a mask layer 103 on a surface of the base 101;

step (S12), patterning the mask layer 103 by a nanoimprinting andetching method;

step (S13), patterning the surface of the base 101 by an etching methodto form a plurality of three-dimensional nano-structure preforms 1021;

step (S14), forming a plurality of three-dimensional nano-structures 102by removing the mask layer 103.

In step (S10), the base 101 can be an insulative base or a semiconductorbase. The base 101 can be made of a material such as glass, quartz, Si,SiO₂, Si₃N₄, GaN, GaAs, Al₂O₃, or MgO. The base 101 can also be made ofa doped material such as doped N-type GaN or P-type GaN. The base 101can be cleaned in a clean room.

In step (S11), the mask layer 103 can be a single layered structure or amulti-layered structure. The thickness of the mask layer 103 can beselected according to the etching depth or the etching atmosphere. Thepatterned mask layer 103 formed in the following steps will have a highprecision. If the mask layer 103 is a single layered structure, thematerial of the mask layer 103 can be ZEP520A which is developed by ZeonCorp of Japan, HSQ (hydrogen silsesquioxane), PMMA(Polymethylmethacrylate), PS (Polystyrene), SOG (silicon on glass) andother silitriangle oligomers. The mask layer 103 is used to protect aportion of the base 101. In one embodiment, the mask layer 103 is amulti-layered structure. The mask layer 103 includes a first mask layer1032 and a second mask layer 1034 stacked on the base 101 in that order,with the second mask layer 1034 covering the first mask layer 1032. Thefirst mask layer 1032 and the second mask layer 1034 can be selectedaccording to need. The material of the first mask layer 1032 can beZEP520A, PMMA, PS, SAL601 and ARZ720. The material of the second masklayer 1034 can be HSQ, SOG, and other silitriangle oligomers. The secondmask layer 1034 can be easily printed by a mechanical method to ensureprecision of the mask layer 103. In one embodiment, the material of thefirst mask layer 1032 is ZEP520A, and that of the second mask layer 1034is HSQ. The first mask layer 1032 and the second mask layer 1034 can beformed by a screen printing method or a deposition method.

The step (S11) includes sub-steps of:

step (S111), forming the first mask layer 1032; and

step (S112), forming the second mask layer 1034.

In step (S111), the first mask layer 1032 is formed by the followingsteps. First, the base 101 is cleaned in a clean room. A layer ofpositive electron-beam resist can be spin-coated on the base 101 at aspeed of about 500 rounds per minute to about 6000 rounds per minute,for about 0.5 minutes to about 1.5 minutes. The positive electron-beamresist can be ZEP520A resist, which is developed by Zeon Corp of Japan.The base 101 with the positive electron-beam resist can be dried at atemperature of about 140 degrees centigrade to 180 degrees centigrade,for about 3 minutes to about 5 minutes, thereby forming the first masklayer 1032 on the base 101. The thickness of the first mask layer 1032can be in a range of about 100 nanometers to about 500 nanometers.

In step (S111), the mask layer 1034 can be a layer of HSQ resist. TheHSQ resist is spin-coated on the first mask layer 1032 under highpressure at a speed of about 2500 rounds per minute to about 7000 roundsper minute, for about 0.5 minutes to about 2 minutes. The thickness ofthe second mask layer 1032 can range from about 100 nanometers to about300 nanometers. The HSQ can be pressed to deform at room temperature.Moreover, the HSQ has good structural stability, and provides a highresolution, often better than 10 nm.

Furthermore, a transition layer (not shown) can be deposited on thefirst mask layer 1032 before the step of forming the second mask layer1034. In one embodiment, the transition layer can be a glassy silicondioxide film with a thickness of about 10 nanometers to about 100nanometers. The transition layer is used to protect the first mask layer1032 during nanoimprinting the second mask layer 1034.

In step (S12), the mask layer 103 can be patterned by the followingsteps:

step (S121), providing a patterned template 200;

step (S122), attaching the template 200 on the second mask layer 1034,and pressing and removing the template 200 to form a plurality of slotson the second mask layer 1034;

step (S123), removing the residual second mask layer 1034 in the bottomof the slot to expose the first mask layer 1032; and

step (S124), patterning the mask layer 103 by removing one part of thefirst mask layer 1032 corresponding with the slots.

In step (S121), the template 200 can be made of rigid materials, such asnickel, silicon, and carbon dioxide. The template 200 can also be madeof flexible materials, such as PET, PMMA, polystyrene (PS), andpolydimethylsiloxane (PDMS). The template 200 can be fabricated throughan electron beam lithography method with the nano-pattern formedtherein. The template 200 includes a plurality of protruding structures.The protruding structures are substantially parallel with and spacedfrom each other to form an array, concentric circles, or concentricrectangles. A slot is defined between the two adjacent protrudingstructures. The protruding structures form the nano-pattern of thetemplate 200. The nano-pattern can be designed according to the actualapplication. In one embodiment, the protruding structures are bar-shapedextending substantially along the same direction. The width of theprotruding structure and that of the slot can be substantially the same.In one embodiment, both the width of the protruding structure and thatof the slot range from about 50 nanometers to about 200 nanometers.

In step (S122), the template 200 is pressed towards the base 101 at roomtemperature. During this process, the protruding structures are pressedinto the second mask layer 1034 to form a plurality of slots in thesecond mask layer 1034, and some materials of the second mask layer 1034remain at the bottom of the slot. Finally, the template 200 is removed,with only the nano-pattern remaining in the second mask layer 1034. Thenano-pattern of the second mask layer 1034 includes a plurality ofsecond protruding structures and a plurality of slots. The protrudingstructures in the second mask layer 1034 correspond to the slots in thetemplate 200. The slots in the second mask layer 1034 correspond to theprotruding structures in the template 200.

In one embodiment, the template 200 is pressed towards the base 101 atroom temperature in a vacuum environment of about 1×10⁻¹ millibars toabout 1×10⁻⁵ millibars. The pressure applied on the template 200 isabout 2 pounds per square foot to about 100 pounds per square foot. Thepressure is applied on the template 200 for about 2 minutes to about 30minutes. There may be material of the second mask layer 1034 remainingat the bottom of the slots.

In step (S123), the residual material of the second mask layer 1034 atthe bottom of the slots can be removed by plasma etching. In oneembodiment, a CF₄ reactive plasma etching method can be used to removethe remaining material of the second mask layer 1034 at the bottom ofthe slots. For example, the base 101 with the protruding structures andthe slots formed in the second mask layer 1034 can be placed in a CF₄reactive plasma etching system. The CF₄ reactive plasma etching systemgenerates CF₄ plasma, and the CF₄ plasma then moves towards the secondmask layer 1034. The material of the second mask layer 1034 remaining atthe bottom of the slots will be etched away, so that the first masklayer 1032 corresponding to the slots will be exposed. At the same time,the width of the top of the protruding structures in the second masklayer 1034 is decreased during the etching process. However, thenano-pattern in the second mask layer 1034 will be maintained.

In step (S124), the first mask layer 1032 exposed by the slots can beremoved by oxygen plasma etching. For example, the base 101 after beingtreated by step (S123) can be placed in an oxygen plasma etching system.The power of the oxygen plasma etching system can in a range of about 10watts to about 150 watts. The speed of the oxygen plasma can be about 2sccm to about 100 sccm. The partial pressure of the oxygen plasma can beabout 0.5 Pa to about 15 Pa. The etching time can be about 5 seconds toabout 1 minute. During the process of etching the first mask layer 1032,the first mask layer 1032 exposed by the slots will be removed, and thebase 101 corresponding to the slots will be exposed. The protrudingstructures in the second mask layer 1034 function as a mask to theoxygen plasma to ensure the resolution of the first mask layer 1032.

During the etching process, the pattern in the second mask layer 1034will be copied onto the first mask layer 1032 to form a patterned masklayer 103. The patterned mask layer 103 includes a plurality ofprotruding structures 1031 on the surface of the base 101. Eachprotruding structure 1031 includes the first mask layer 1032 and thesecond mask layer 1034 stacked together. A slot 1033 is defined betweenevery two adjacent protruding structures 1031, and the surface of thebase 101 corresponding to the slot 1033 is exposed. During the processof etching the first mask layer 1032, the top of the protrudingstructures of the second mask layer 1034 will also be partly etched. Thenano-pattern in the second mask layer 1034 can still be maintainedbecause the speed of etching the second mask layer 1034 is much smallerthan that of the first mask layer 1032. Thus, the resolution of the masklayer 103 can be improved.

In step (S13), the base 101 after step (S12) can be placed in aninductively coupled plasma device to etch the base 101 exposed by themask layer 103. The etching gas can be selected according to thematerial of the base 101 and the mask layer 103. During the etchingprocess, the surface of the base 101 exposed by the slots 1033 of themask layer 103 will be etched, thereby forming a plurality of grooves inthe base 101.

Referring to FIG. 5 and FIG. 6, the etching process includes thefollowing substeps:

first stage, form a plurality of grooves with the same depth by etchingthe surface of the base 101 with the etching gas;

second stage, continuing the etching process so that every two adjacentprotruding structures 1031 begin to slant face to face to form aprotruding pair; and

third stage, continuing the etching process so that the two adjacentprotruding structures 1031 gradually slant until the tops of the twoadjacent protruding structures 1031 contact each other.

In the first stage, the etching gas etches the exposed surface of thebase 101 to form a plurality of grooves. The grooves have the same depthbecause of the same etching speed.

In the second stage, during the etching process, the etching gas willreact with the base 101 to form a protective layer. The protective layerwill reduce the etching speed of the base 101, and the width of thegrooves will slowly decrease from the outer surface of the base 101 tothe bottom of the grooves. Thus, the inner wall of the grooves will benot absolutely perpendicular to the surface of the base 101, but form anangle. The etching gas not only etches the base 101, but also etches thetop of the protruding structures 1031. The width of the top of theprotruding structures 1031 will decrease. The resolution of the masklayer 103 will not be affected because the speed of etching the top ofthe protruding structures 1031 is much smaller than that of the base101. Furthermore, every two adjacent protruding structures 1031 willslant face to face.

In the third stage, the tops of the two adjacent protruding structures1031 will gradually approach to each other. The speed of etching thebase 101 corresponding to these two closed adjacent protrudingstructures 1031 will decrease, and the width of the grooves willgradually decrease from the outer surface of the base 101 to the bottomof the grooves of the base 101. Because the two adjacent protrudingstructures 1031 slant face to face to form a protruding pair, the speedof etching the base 101 corresponding to the protruding pair willfurther decrease. Eventually, the tops of the two adjacent protrudingstructures 103 contact each other, and the etching gas can no longeretch the base 101 corresponding to the two adjacent protrudingstructures 103, thus the first groove 1026 is formed on the surface ofthe base 101. But between every two adjacent protruding pairs, theetching speed will change less than the slant two adjacent protrudingstructures 1031. Thus the second grooves 1028 are formed, and the depthof the second grooves 1028 will be greater than that of the firstgrooves 1026. The plurality of three-dimensional nano-structure preforms1021 is obtained on the substrate 100.

In one embodiment, the etching gas includes Cl₂, BCl₃, O₂ and Ar. Thepower of the inductively coupled plasma device ranges from about 10watts to about 100 watts, the flow speed of the etching gas ranges fromabout 8 sccm to about 150 sccm, the pressure of the etching gas canrange from about 0.5 Pa to about 15 Pa, and the etching time can rangefrom about 5 seconds to about 5 minutes. In the etching gas, the flowspeed of the Cl₂ ranges about 2 sccm to about 60 sccm, the flow speed ofthe BCl₃ ranges from about 2 sccm to about 30 sccm, the flow speed ofthe O₂ ranges from about 3 sccm to about 40 sccm, and the flow speed ofthe Ar ranges from about 1 sccm to about 20 sccm. In one embodiment, theflow speed of the etching gas ranges from about 40 sccm to about 100sccm to improve the resolution and the etching speed. In anotherembodiment, the power of the inductively coupled plasma device is about70 watts, the flow speed of the etching gas is about 40 sccm, thepressure of the etching gas is about 2 Pa, and the etching time is about2 minutes. In the etching gas, the flow speed of the Cl₂ is about 26sccm, the flow speed of the BCl₃ is about 16 sccm, the flow speed of theO₂ is about 20 sccm, and the flow speed of the Ar is about 10 sccm.

The mask layer 103 and the etching gas are not limited as describedabove. The etching gas can include one gas or a mixture of differentgases, so long as the tops of the two adjacent protruding structures1031 in the mask layer 103 can be closed. The flow speed of the etchinggas, the pressure, the etching time, and the ratio between the differentgases can be can be dependent upon the three-dimensional nano-structure102.

In step (S14), the three-dimensional nano-structure 102 can be obtainedby dissolving the mask layer 103. The mask layer 103 can be dissolved ina stripping agent such as tetrahydrofuran (THF), acetone, butanone,cyclohexane, hexane, methanol, or ethanol. In one embodiment, thestripping agent is butanone, and the mask layer 103 is dissolved inbutanone and separated from the base 101. The mask layer 103 is removedto form the substrate 100 and the plurality of three-dimensionalnano-structures 102 located on the substrate 100. The plurality ofthree-dimensional nano-structures and the substrate 100 are integratedto form an integrated structure.

The method for making the three-dimensional structure has the followingadvantages. First, the second mask layer is made from the HSQ resist,which can be imprinted at room temperature, and the HSQ has smalldeformation in the subsequent manufacturing process, thereby ensuringthe accuracy of subsequent etching. Second, the first mask layer issandwiched between the substrate and the second mask layer, and thesecond mask layer will protect the first mask layer in the etchingprocess to ensure good resolution of the first mask layer. Third, thenano-imprinting method can be carried out at room temperature, and thetemplate does not need pre-treatment. Thus, the method is simple and lowin cost. Fourth, the plurality of M-shaped three-dimensional structurescan be easily formed on the substrate, and the productivity of thepatterned substrate can be improved. Fifth, the mask layer can beselected according to the material of the substrate to etch differentkinds of substrates.

Referring to FIG. 7 and FIG. 8, a three-dimensional nano-structure array20 of one embodiment includes a substrate 100 and a number ofthree-dimensional nano-structures 202 located on at least one surface ofthe substrate 100. Each three-dimensional nano-structure 202 is anM-shaped structure. The three-dimensional nano-structures 202 aresimilar to the three-dimensional nano-structures 102, except that theplurality of three-dimensional nano-structures 202 is aligned side byside and extends to form a plurality of concentric circles. Each of theplurality of three-dimensional nano-structures 202 is a double-peakstructure including two peaks, and the three-dimensional nano-structure202 forms a circle. The cross-section of the three-dimensionalnano-structures 202 is M-shaped. The plurality of three-dimensionalnano-structures 202 can cover the entire surface of the substrate 100.

Referring to FIG. 9 and FIG. 10, one embodiment of a three-dimensionalnano-structure array 30 includes a substrate 100 and a number ofthree-dimensional nano-structures 302 located on at least one surface ofthe substrate 100. Each of the three-dimensional nano-structures 302 isan M-shaped structure. The three-dimensional nano-structure 302 issimilar to the three-dimensional nano-structures 102, except that theplurality of three-dimensional nano-structures 302 is aligned side byside and extends to form a plurality of concentric rectangles. Eachthree-dimensional nano-structure 302 is a double-peak structureincluding two peaks, and the three-dimensional nano-structure 302 formsa rectangle. The cross-section of the three-dimensional nano-structures302 is M-shaped. The plurality of three-dimensional nano-structures 302can cover the entire surface of the substrate 100.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the disclosure. Any elements describedin accordance with any embodiments is understood that they can be usedin addition or substituted in other embodiments. Embodiments can also beused together. Variations may be made to the embodiments withoutdeparting from the spirit of the disclosure. The above-describedembodiments illustrate the scope of the disclosure but do not restrictthe scope of the disclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A three-dimensional nano-structure array,comprising: a substrate having a plurality of three-dimensionalnano-structures, wherein each of the three-dimensional nano-structureshas a first peak and a second peak aligned side by side, a first grooveis defined between the first peak and the second peak, a second grooveis defined between every two adjacent three-dimensional nano-structuresof the three-dimensional nano-structures, and a depth of the firstgroove is smaller than a depth of the second groove.
 2. Thethree-dimensional nano-structure array of claim 1, wherein eachthree-dimensional nano-structure is a bar-shaped protruding structureextending along a straight line, a curvy line, or a polygonal line. 3.The three-dimensional nano-structure array of claim 1, wherein across-section of each three-dimensional nano-structure is M-shaped. 4.The three-dimensional nano-structure array of claim 1, wherein across-section of the first peak is trapezoidal or triangular, and across-section of the second peak is trapezoidal or triangular.
 5. Thethree-dimensional nano-structure array of claim 1, wherein the firstpeak comprises a first surface and a second surface intersected witheach other to form a first include angle, and the second peak comprisesa third surface and the fourth surface intersected with each other toform a second include angle, both the first include angle and the secondinclude angle range from about 30 degrees to about 90 degrees.
 6. Thethree-dimensional nano-structure array of claim 1, wherein both thefirst peak and the second peak have the highest point, a distancebetween the highest point of the first peak and the highest point of thesecond peak is smaller than a width of each three-dimensionalnano-structure.
 7. The three-dimensional nano-structure array of claim6, wherein the width of each of the three-dimensional nano-structuresranges from about 100 nanometers to about 300 nanometers.
 8. Thethree-dimensional nano-structure array of claim 1, wherein a distancebetween every two adjacent three-dimensional nanostructures of thethree-dimensional nano-structures is substantially equal.
 9. Thethree-dimensional nano-structure array of claim 8, wherein the distancebetween every two adjacent three-dimensional nanostructures of thethree-dimensional nano-structures ranges from about 0 nanometers toabout 200 nanometers.
 10. The three-dimensional nano-structure array ofclaim 1, wherein the plurality of three-dimensional nano-structures isperiodically aligned, and a period of the plurality of three-dimensionalnano-structures ranges from about 100 nanometers to about 500nanometers.
 11. The three-dimensional nano-structure array of claim 1,wherein a cross-section of the first groove is V-shaped.
 12. Thethree-dimensional nano-structure array of claim 11, wherein the depth ofthe first groove ranges from about 30 nanometers to about 120nanometers.
 13. The three-dimensional nano-structure array of claim 1,wherein a cross-section of the second groove is V-shaped or inversetrapezium.
 14. The three-dimensional nano-structure array of claim 13,wherein the depth of the second groove ranges from about 100 nanometersto about 200 nanometers.
 15. The three-dimensional nano-structure arrayof claim 1, wherein the plurality of three-dimensional nano-structuresand the substrate are integrated to form an integrated structure. 16.The three-dimensional nano-structure array of claim 1, wherein theplurality of three-dimensional nano-structures is aligned side by sideand extends to form a plurality of concentric circles.
 17. Thethree-dimensional nano-structure array of claim 1, wherein the pluralityof three-dimensional nano-structures is aligned side by side and extendsto form a plurality of concentric rectangles.
 18. The three-dimensionalnano-structure array of claim 1, wherein the first groove, the secondgroove, the first peak and the second groove extend substantially alongthe same direction.
 19. A three-dimensional nano-structure array,comprising: a substrate comprising a surface, and a plurality of firstgrooves and a plurality of second grooves alternately defined in thesurface, the plurality of first grooves and the plurality of secondgrooves extending substantially along the same direction, and a depth ofthe first groove is lower than a depth of the second groove.
 20. Athree-dimensional nano-structure array, comprising: a substratecomprising a plurality of three-dimensional nano-structures, wherein theplurality of three-dimensional nano-structures are aligned side by side,and extend along the same direction, and a cross-section of eachthree-dimensional nano-structure is M-shaped.